Method of and apparatus for sterilizing a web material



April 22, 1969 A. 'ruMA 3,440,003

METHOD 0F AND APPARATUSA FOR STERILIZING A WEB MATERIAL Filed Aug. 16, 196e snm g Qf 2 INVENTOR A LE X T U M A ATTORNEY United States Patent Office The present invention relates to a method of sterilizing at least one side of -a web materia-l, which is meant to be f used for manufacturing packages by shaping them into tubes and then sealing the shaped tube transversely.

Previously, such sterilizing took place preferably by moving the web-like packaging material -through a bath of a sterilizing liquid. In that connection there were difficulties chiefly with regard to the guiding of the web of material when a new web was to be inserted. Furthermore, there were diiculties in connection with the .removal and destruction of bacteria-protecting spots, e.g. of milk or oil. The method according to the present invention, which aims atlsolving these problems, is chiefly characterized in that the web of material is pressed with at least that side which is to form the inner side of the package against a pad or mat of material which is steeped in sterilizing liquid, is porous and preferably compressible, e.g. foam rubber or foam plastic, which is supplied with sterilizing liquid from a storage vessel for such liquid, which has been heated completely or partly by means of a heating element to a suitable sterilizing temperature, and is further characterized in tha-t liquid which may possibly remain after the sterilizing operation is rep moved.

When packaging food in particular it is essential that all sterilizing liquid is removed. According to the present invention this can be brought about in two different ways; it may for instance take place by keeping that end of the said pad or mat which was the last to leave contact with the web of material at a temperature which is at least equal to the boiling-point of the sterilizing liquid.

Alternatively, liquid remaining after the sterilizing operation may be removed from .the web of material by means of air orifices directed` obliquely against the web and acting as air knives. The latter alternative has the advantage of making it possible -to avoid that solid or dissolved particles coming from the liquid will remain on the sterilized side of the packaging material.

The invention also comprises a device for putting lthe method described above into effect, the said device being characterized by a pad or mat of -a porous, preferably compressible material which can be pressed against the webalike packaging material -and is adapted to be steeped in sterilizing liquid from a storage container for such liquid and which is in direct or indirect contact with a heating element for heating to a suitable steril-izing temperature. For lthis purpose, either the whole pad or part of it can be heated.

Further particulars and advantages of the invention will be lapparent from the accompanying drawing, FIGS. 1 and 2 showing two preferred embodiments of the invention, chosen by way of example.

In the embodiment shown in FIG. 1 a web of material 1 is introduced between a pressing plate 2 and a pad 3 and is la-id around a roller 4, whence the web is moved to means known per se and `therefore not shown for shaping the web into a tube and seal-ing the said tube transversely so as to form sepa-rate packages. At its lower end the p-ad 3 is immersed into a vessel 5 holding the sterilizing liquid 6, which is absorbed into the pad by 3,440,003 Patented Apr. 22, 1969 the capillary forces acting therein. The trailing contact of the web 1 with the pad 3 also contributes to absorbing the liquid into the pad. The -sterilizing liquid may be e.g., hydrogen peroxide, H2O2, or sodium hypochlorite, NaClQ. In order to maintain a constan-t liquid level in the vessel 5 there is a filling vessel 7 which is completely closed except for an orifice immersed into the liquid 6. The pressing plate 2 is displaceable in the direction of the double arrow A. As a result hereof it can either be moved into contact with the web 1 for pressing the web 'against the pad 3, which in that connection supports itself on the -supporting plate 8, or be completely moved aside, e.g. when a new web of material is lto be fed into the machine. In the latter position the web of material can very easily be changed. Reference numerals `9 and 10 designate two diagrammatically shown elements by meaiis of which the upper end of the pad 3 can -be heated to a suit-able sterilizing temperature. In certain c-ase-s it may be sui-table to let these elements extend along the whole length of the pad 3. In other cases it may be advisable to exclude one of the elements. In lthe embodiment shown it is importan-t, however, that the elements 9 and 10 have such an effect that the top end of the pad 3 is heated at leas-t to the boiling point of the sterilizing liquid.` This ensures that no sterilizing liquid will enter the finished packages. The rol-ler 4 and the tube shaping and. transverse sealing means not shown in FIG. 1 are preferably enclosed in an essentially completely sterilized space, diagrammatically outlined in the figure by =a rectangle .11 drawn in dashed lines. The pressing plate 2 on one hand and the pad 3 on the other can be said to constit'ute the two longitudinal sides of a slot-shaped inlet orifice 12 to this space 11. In order to ensure that the sterilized space 11 is not reinfeoted by the outside of the packaging material it is possible to have this side, too, of the web sterilized by replacing the pressing plate 2 with a device facing the devices 3, 5, 6, 7 and 8, one of these devices having to be mobile in the same way as the pressing plate 2.

In the device shown in FIG. 2 a web-like pack-aging material 1a is fed in the same way between a pressing plate 2a and -a pad 3a to a roller 4a and thence to known and therefore not shown means for shaping the material into a tube and seal-ing the tube transversely. The pad 3a is immersed into a vessel 5a containing sterilizing liquid 6a, which is absorbed into the pad 3a by the capillary forces acting therein, The pressing plate 2a is displace- 'able in the direction of the double arrow A into and out of `contact with the packaging material 1a. Two springs 13a are provided for generating the contact pressure against the web 1a. The supporting plate designated 8 in FIG. 1 has its equ-ivalent in FIG. 2 in a double-jacketed supporting plate 8a which is adapted to enclose a heating element 9a in it. In the same way as in the device according to FIG. 1 the roller 4a and the subsequent shaping means which are known per se and therefore not shown are enclosed in a sterilized chamber 11a outlined diagrammatically by a rectangle of dashed lines. The embodiment according to FIG. 2 differs from the one according to FIG. 1 above all on account of the sterilizing liquid not' being heated to its boiling-point. Instead, after the sterilizing operation proper, sterilizing liquid remaining on the packaging material is removed by means of air nozzles 14a directed obliquely agains-t the web of material and acting as air knives, said nozzles effectively removing all liquid from the packaging material. For this purpose the liquid is caused to drip into a channel 15a through which it flows back down into the vessel 5a.

Of course, the invention is not restricted -to the embodiments described above but may be varied within the scope of the appended claims. For instance, the capillary forces acting in the pad 3 or 3a may not always be sulficient for producing effective wetting of the web of material. For that purpose it is possible either to move the vessel 5 or 5a upward so that an automat-ic pressure will be generated as a result of the location of the vessel in relation to the pad, or to generate this pressure by means of a suitable pumping device. In order to produce even heating of the web 3a it may be advisable to ll the double-jacketed supporting plate 8a with liquid, e.g. water. In order to avoid scraping between the pressing plate 2 or 2a and the web of material 1 or 1a it is possible to shape the former according to the principles applying to so called hovercraft, i.e. create an air cushion between the plate and the web. In certain cases it maybe advisable to let the whole heating operation take place Ithrough the treated material, i.e., to exclude the element 9 in the device according to FIG. 1. In that connection only the surface layer of the pad 3 resting against the web of material is heated, and the greater portion of the processing liquid does not therefore, have to be heated.

The method according to the invention has turned out to be very efficient. This is probably due to the fact that this method provides a combination of mechanical, chemical and thermal sterilizing, i.e. the pad scrapes against the packaging material at lthe same time as the said material is treated by the heated sterilizing liquid.

That which is claimed is:

1. A method of sterilizing at least one side of a web material comprising the steps of providing a porous pad of compressible material, steeping said pad with sterilizing liquid from a storage vessel, heating said sterilizing liquid to a suitable sterilizing temperature, running said web material with one face thereof against said pad and removing ster-ilizing material from said one face of said material after contact with said pad.

2. The method of claim 1 wherein said face of said material leaving contact with said pad is maintained at a temperature at least equal to the boiling point of said sterilizing liquid.

3. The method of claim 1 wherein said sterilizing liquid is removed from one face of said material by directing air from a plurality of air nozzles against said face of said material.

4. Apparatus to sterilize at least one face of a web material comprising: a supply of web material, a pad of compressible porous material adjacent said web of material, a supply of sterilizing liquid operably associated with said pad, means heating said sterilizing liquid to a suitable sterilizing temperature, and means moving past and pressing one face of said web material against said pad to sterilize said face.

5. The structure of claim 4 wherein means are provided to remove excess sterilizing liquid from the surface of said web material previously pressed against said pad.

I6. The structure of claim S wherein said means removing said liquid from said web material is air nozzle means directing a ow of air obliquely against the sterilized surface of said web material.

7. The structure of claim 5 wherein said web material from said pad is supplied into a sterilized chamber from said pad, said sterilized chamber enclosing said pad and having a slot shaped opening therein for the passage of said web material.

8. The structure of claim 5 wherein a second sterilizing pad is provided adjacent the other face of said web material to complete sterilization of both sides of said web material.

9. The structure of claim 5 wherein said means removing said liquid from said web material is heating means heating said web material to at least the boiling temperature of the sterilizing liquid at a point where the web material leaves contact with said pad.

10. The structure of claim 9 wherein said heating means are heating elements on both sides of said web material.

References Cited UNITED STATES PATENTS 2,200,289 5/1940 Moore 118-268 XR 3,157,900 11/1964 Thompson 118-268 XR MORRIS O. WOLK, Primary Examiner.

D. G. MILLMAN, Assistant Examiner.

U.S. Cl. X.R. 21-92; 118-268 

1. A METHOD OF STERILIZING AT LEAST SIDE OF A WEB MATERIAL COMPRISING THE STEPS OF: PROVIDING A POROUS PAD OF COMPRESSIBLE MATERIAL, STEEPING SAID PAD WITH STERILIZING LIQUID FROM A STORAGE VESSEL, HEATING SAID STERILIZING LIQUID TO A SUITABLE STERILIZING TEMPERATURE, RUNNING SAID WEB MATERIAL WITH ONE FACE THEREOF AGAINST SAID PAD AND REMOVING STERILIZING MATERIAL FROM SAID ONE FACE AND SAID MATERIAL AFTER CONTACT WITH SAID PAD. 